That happens to me as well sometimes...

probably your account has an error. And people would have to flag wisely on post and comments that are  Inappropriate!

Hello @All! 

According to what I can say due to this issue is that your account has to go through a support quere to verify that your activity tab can display your flag count. Here is a post related to this https://support.khanacademy.org/hc/en-us/community/posts/115006257627-profile-flag in the 'Help Centre'. You can get help or understand more. Graphipedia, the problem does not come from accpunt error; A user might also be flagged once that may occur that situation.

-Hope this helps, 

~Galaxy